The invention relates to an illumination device for a motor vehicle.
Scanning lighting systems for motor vehicles are known from the prior art. The scanning lighting systems use a scanner to deflect a light beam created by at least one semiconductor diode in a suitable manner to yield different light distributions. In general, line scanners perform a line-by-line scan of the illumination area in which the light distribution is to be created at a fixed scanning speed and in a fixed scanning pattern. To create different light distributions, the light output of the semiconductor diodes is varied or the diodes are switched on and off.
Traditional scanning illumination devices have the disadvantage that the semiconductor diodes for generating the predefined light distribution are not operated at full power at all points in time, which means that the light source is not used at its maximum cost/benefit efficiency. To create a light distribution with great detail and precision and a high contrast, a high-frequency scanner scan and a high-frequency modulation of the intensity of the semiconductor diodes over time are also necessary, which in turn presupposes a complex and expensive electronic control system for the illumination device.
The object of the invention is to create a scanning illumination device for a motor vehicle with which a predefined light distribution is generated easily and efficiently.
This and other objects are achieved by an illumination device according to the invention comprising a light source formed of a number of semiconductor diodes and a scanner, on which a beam of light generated by the light of the light source falls. The scanner changes the position of the light beam during operation of the illumination device and thereby moves a light spot created by the light beam at a distance from the illumination device and, in particular, in a high beam of the illumination device. With the moving light spot, a predefined light distribution is generated by use of corresponding control equipment. A plurality of different predefined light distributions can preferably be generated with the illumination device through appropriate control of the control equipment. The term “high beam” is understood to refer to the light distribution at a distance from the illumination device which is much larger than the dimensions of the illumination device, in particular in the range of 25 meters in front of the illumination device. A light beam is understood to be a bundle of light rays limited in angle and/or in space such that the rays of light in the bundle may be essentially parallel or may converge or diverge. The light beam may be created by the light source itself and/or optionally also by one or more optical units between the light source and the scanner.
In contrast with traditional scanning illumination devices, the illumination device according to the invention is designed so that the scanning speed at which the light spot is moved, the scanning path along which the light spot is moved, and/or the size of the light spot can be varied and controlled with suitable control equipment to generate the predefined light distribution. The scanning path corresponds to the pattern of movement of the light spot, which is created by the change in position of the light beam. Through a corresponding definition of a scanning path, the range in which a predefined light distribution occurs can be limited. Furthermore, by passing over the same regions repeatedly according to the defined scanning path, the light intensity in these regions can be increased accordingly.
The illumination device according to the invention has the advantage that due to the available scanning speed, the variable scanning path, and/or the variable light spot size, a predefined light distribution can be adjusted easily and can also be varied, if necessary, while the light distribution is being generated without thereby having to have an influence on the light efficiency of the semiconductor diodes. Any desired light distributions can be implemented with no problem in this way. Furthermore, the scanning speed can be reduced in comparison with traditional line scanners, so that problematical motion effects are prevented.
In a particularly preferred embodiment, a predefined light distribution with locally variable light intensity can be generated with this illumination device, such that the scanning speed is reduced in regions of a predefined light distribution with a high light intensity and/or the light spot passes regions of the predefined light distribution with a higher light intensity more frequently according to the scanning path.
In another embodiment of the illumination device according to the invention, a predefined light distribution with a locally varied resolution can be generated, such that the size of the light spot is reduced in regions of the predefined light distribution with a higher local resolution.
In a particularly preferred embodiment, a laser light source is used as the light source in the illumination device according to the invention. This means that the semiconductor diodes include one or more laser diodes, and in particular only laser diodes. A distribution of light with a very high local light intensity can be created in this way. The laser diodes preferably each have a maximum power of at least 1W and, in particular, between 1.5W and 5W.
In another embodiment, the illumination device according to the invention is designed so that, for generating the predefined light distribution, the numerous semiconductor diodes are operated at a constant power and preferably at maximum power, so that the apparatus is particularly economical to use.
In yet another embodiment of the device according to the invention, the scanner is a vector scanner with which the scanning speed and/or scanning path can be varied in such a way that both the speed and the path can be varied in particular. Thus, the scanning speed and/or scanning path can be varied in a particularly simple manner by using essentially known vector scanners.
In a preferred specific embodiment of the illumination device, an optical unit which the light beam falls onto after passing through the scanner is provided for varying the size of the light spot. This optical unit includes in particular a lens and/or a reflector having a variable focal distance. Such optical elements are known per se and consist of electro-active substances, for example, whose properties change as a result of an electric voltage being applied, such that the focal distance of the lens and/or of the reflector is varied.
In another specific embodiment of the invention, the light source is a monochromatic light source in which a conversion element is provided for converting the light of the light source into white light. Such conversion elements are known per se from the prior art. For example, a phosphorus conversion element made of phosphorus nitride, phosphorus oxynitride or cerium-doped YAG phosphorus may be used with blue/violet laser diodes with an emission wavelength of 450 nm/405 nm to generate white light.
The conversion element, which is designed as a layer in particular, may be arranged in different positions, depending on the embodiment of the invention. The conversion element may be arranged in particular on the light source or between the light source and the scanner. In the latter case, the conversion element is arranged in a position in the path of the light beam before the light beam strikes the scanner. Likewise, however, the conversion element may be arranged in a position in which the light beam has already passed over the scanner.
Depending on the application case, the illumination device according to the invention may assume various functionalities. In one embodiment, the illumination device comprises a headlight. A headlight is characterized in that it actively illuminates the surroundings of a vehicle. The illumination device according to the invention may, if necessary, also comprise a signal light, which is characterized in that it serves only to deliver signals for other traffic participants.
In a preferred variant, the illumination device is designed as a headlight, such that a low-beam light characteristic is generated as a predefined light distribution during operation. This is characterized by a sharp cut-off line (also called a light-dark line), which can be generated easily by controlling the scanning speed, the scanning path and/or the size of the light spot. In particular, the light spot can be reduced in size accordingly in the area of the cut-off line to thereby ensure a high local resolution for this cut-off line. If necessary, the illumination device may also be designed to generate a high-beam characteristic as a predefined light distribution during operation.
In another embodiment of the illumination device according to the invention, a beam limitation device is provided between the light source and the scanner. With this beam limitation device, the cross section of the light beam is limited along a predefined cut-off line. In this case, the illumination device is designed so that one or more cut-off lines are formed with at least one section of the predefined cut-off line in the predefined light distribution. With such an apparatus, sharp cut-off lines can be generated easily due to the predefined limit, which is imaged on the light spot and moves together with it.
In a particularly preferred variant, the beam limitation device comprises an aperture. Then, the cross section of the light beam is limited along the predefined cut-off line by the aperture opening. The aperture may optionally be arranged inside an optical unit, which directs the light beam at the aperture opening and throws the light beam, which is thus directed at the aperture, onto the scanner. This optical unit may comprise, for example, at least one lens in front of the aperture and/or at least one lens downstream from the aperture. Alternatively or additionally, the beam limitation device may also comprise a waveguide, in particular an optical fiber. The cross section of the waveguide in this case determines the limitation of the light beam.
In a preferred variant, the predefined cut-off line, which is created with the beam limitation device, comprises one or more straight lines with which the cut-off line or cut-off lines are formed in the predefined light distribution. The predefined cut-off line is preferably a parallelogram here. With a parallelogram, a low-beam light characteristic can be created over the corresponding directions of its edges, for example. This characteristic usually comprises a straight cut-off line running horizontally in the area of the center of the road surface and a cut-off line running obliquely upward at the edge of the road surface. These cut-off lines can be imaged in the light distribution thereby created by means of corresponding edges of the parallelogram and the movement of the scanner.
In addition to the illumination device according to the invention, the present invention also relates to a motor vehicle which has one or more of the illumination devices according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.